CA2259736C - Membrane air dryer with scheme to reduce air lost as sweep air - Google Patents
Membrane air dryer with scheme to reduce air lost as sweep air Download PDFInfo
- Publication number
- CA2259736C CA2259736C CA002259736A CA2259736A CA2259736C CA 2259736 C CA2259736 C CA 2259736C CA 002259736 A CA002259736 A CA 002259736A CA 2259736 A CA2259736 A CA 2259736A CA 2259736 C CA2259736 C CA 2259736C
- Authority
- CA
- Canada
- Prior art keywords
- gas
- purge valve
- compressor
- dryer
- atmosphere
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000012528 membrane Substances 0.000 title claims abstract description 75
- 238000010926 purge Methods 0.000 claims abstract description 55
- 239000012466 permeate Substances 0.000 claims abstract description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 230000003137 locomotive effect Effects 0.000 claims description 13
- 238000007599 discharging Methods 0.000 claims 2
- 239000007789 gas Substances 0.000 description 21
- 238000001035 drying Methods 0.000 description 16
- 239000000835 fiber Substances 0.000 description 12
- 239000012071 phase Substances 0.000 description 10
- 238000007605 air drying Methods 0.000 description 8
- 239000002274 desiccant Substances 0.000 description 8
- 239000012073 inactive phase Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 230000006870 function Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000005057 refrigeration Methods 0.000 description 2
- 230000001172 regenerating effect Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000007775 late Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/268—Drying gases or vapours by diffusion
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
- B60T17/002—Air treatment devices
- B60T17/004—Draining and drying devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2313/00—Details relating to membrane modules or apparatus
- B01D2313/16—Specific vents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2313/00—Details relating to membrane modules or apparatus
- B01D2313/18—Specific valves
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Drying Of Gases (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
A control system reduces the amount of gas lost as sweep gas from a membrane gas dryer. The membrane gas dryer is of the type that features an inlet end that receives moisture laden gas from a compressor, an outlet end from which dried gas is discharged to a pneumatic component and a drain port from which permeate sweep gas inclusive of permeate water vapor is expelled from the gas dryer. The control system includes a purge valve that is connected to the drain port of the gas dryer and a mechanism that controls the purge valve. The purge valve has a pilot port that responds to pressure by closing the purge valve thereby preventing the permeate sweep gas from exhausting to atmosphere through the drain port. The mechanism controls the purge valve such that (i) when the compressor is unloaded, the mechanism allows flow of the dried gas from the pneumatic component to pressurize the pilot port thereby closing the purge valve and preventing the permeate sweep gas from exhausting to atmosphere and (ii) when the compressor is loaded, the mechanism vents the pilot port to atmosphere thereby opening the purge valve and allowing the permeate sweep gas to exhaust to atmosphere via the drain port of the membrane gas dryer.
Description
z CA 02259736 2001-08-17 MEMBRANE AIR DRYER WITH SCHEME TO REDUCE AIR LOST AS SWEEP
AIR
FIELD OF THE INVENTION
The invention generally re:Lates to gas dryers of the type that use semipermeable membranes to remove moisture from gas in which the moisture is suspended. More particularly, the invention relates to a system that reduces the amount of gas otherwise lost as sweep gas that is used to sweep the accumulated moisture away from the membranes of the gas dryer.
BACKGROUND OF THE IN'rENTION
The following background information is provided to assist the reader to understand the invention described and claimed below. Accordingly, any terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.
It is well known in the air drying art that the amount of moisture suspended in any given volume of air is dependent on both the pressure and temperature of the air contained in that volume. This relationship between pressure, volume and temperature is defined by the various ideal gas laws of thermodynamics. When a quantity of air is compressed by reducing the volume it occupies, the amount of moisture that the compressed air can hold is reduced accordingly, assuming its temperature is held constant. The temperature of air, however, increases as the air is compressed, and this temperature increase enables the air to hold its moisture.
In most compressed air systems, such as those used in the railroad industry, temperature increases are undesirable. This is because the compressed air system has components downstream whose temperatures may be lower than that of the incoming moisture-laden compressed air. The moisture in such moisture-laden air tends to condense on the surfaces of these downstream components and contaminates the compressed air system and the pneumatic components that it supplies. Consequently, an aftercooler is typically inserted between the output of the compressor and the intake port of the air drying system to lower the temperature of the incoming compressed air. By lowering the temperature, the aftercooler causes some of the water vapor suspended in the air to precipitate out of the air in the form of liquid condensate. This liquid condensate is usually removed from the air drying system via well known devices such as separating chambers and coalescing elements. Despite the use of aftercoolers, separating chambers and coalescing elements, the compressed air will still hold some water vapor as it is difficult to remove this remaining moisture solely by mechanical means. Such mechanical means thus are often used in conjunction with one of the known air drying methods to remove this remaining water vapor. Depending on the specific application and environment in which it is used, an air drying method may be used alone, without the aforementioned mechanical means.
There are at least three prior art methods of drying air that are commonly used to remove water vapor. (1) Absorbent type air dryers use deliquescent desiccant that becomes liquid by absorbing moisture suspended in the air.
Deliquescent air dryers typically have no moving parts and their costs are initially low. These dryers, however, exhibit limited dew point suppression - 20° to 30° F is common. They also require considerable maintenance, e.g., the desiccant must be periodically replaced and the system manually drained on a regular basis. (2) Adsorbent type air dryers use regenerative desiccant that temporarily adsorbs moisture on the surface of its molecules. The moisture temporarily accumulated by the desiccant is later removed via a stream of dried air redirected through the desiccant to purge the moisture to atmosphere. Regenerative dryers are able to achieve low dew points, but impose high costs initially and high operating costs thereafter. Their desiccant towers, in which the desiccant is housed, also must be serviced periodically. (3) Refrigeration type air dryers typically require low maintenance and impose low operating costs, but are not able to achieve low dew points. Dew points are typically limited to approximately 38° F as a minimum to prevent freeze ups. Refrigeration type dryers are used in many industries as a first step in a multi-step drying system, e.g., before drying the air in desiccant type air dryer.
Another method of drying air employs the use of semipermeable membranes to remove moisture from the air in which the moisture is suspended. These membrane type air dryers have long been used in various industries. Such membrane type air dryers typically feature a membrane fiber bundle and a containment vessel or shell in which the bundle is encased. The membrane fiber bundle is of a type that is commercially available from Bend Research, Inc. of Bend, Oregon, U.S.A.
Regarding basic operation of a membrane type air dryer, air passes through each membrane in the bundle by a combination of (i) diffusion through the pores linking the respective surfaces of a membrane and (ii) permeation through the material of the membrane. The force that drives the separation of water vapor from air is the difference between the pressure of the air on one side of a membrane and the pressure of air on the other side of the membrane. When air is compressed, the partial pressures of the various constituents in the air each increase. Water vapor, of course, is present in the stream of compressed air that flows into the inlet of the membrane housing from the source of compressed air. The partial pressure of the water vapor in the air stream flowing in the bundle will be greater than that of the atmospheric air by a factor dependent upon the compression ratio of the compressor. This difference in the partial pressure of water vapor on the inside (higher) versus that on the outside (lower) of the membranes drives the water vapor through the membranes into the sweep air space defined between the outside of the bundle and the inner wall of the containment vessel.
The vessel in which the membrane fiber bundle is encased also features a drain hole that communicates with the sweep air space. The sweep air space serves as the conduit to transport the water vapor that has permeated through the membranes to the drain hole. It is through this drain hole that the permeated water vapor is forcibly purged from the sweep air space by "sweep air." The air stream flowing through the fiber bundle causes pressure to build within its membranes. The "sweep air" that is used to purge the permeated water vapor from the vessel originates within these pressurized membranes. Composed of light gases including even hydrogen and helium that are capable of penetrating the membranes, the sweep air leaks out of the membranes and forcibly carries with it the permeated water vapor out the drain hole in the bottom of the vessel. It is for this reason that the vessel is often referred to as the sweep air containment vessel. The dried non-permeate air that emerges from the outlet of the membrane housing, of course, flows into whatever pneumatic components) that the membrane air dryer is intended to supply.
The membrane type air dryer is typically incorporated within a compressed air system between the source of compressed air and a reservoir or other pneumatic component to which it supplies the compressed dried air. As shown in Figure 1, a check valve is commonly installed between the outlet of the dryer and the inlet of the reservoir to prevent air from flowing back into the dryer when the source of compressed air is unloaded (i.e., turned off). When the source of compressed air is loaded, the compressed air that flows through the fiber bundle will cause pressure to build within the membranes as described previously. It is this pressure that is the source of the sweep air. When the source of compressed air is unloaded, however, the pressure that has accumulated within the membranes is largely lost as sweep air as it is continuously vented from the drain hole of the vessel.
It is well known that on a train locomotive the compressor is controlled so that compressed air is supplied to the air system on a periodic basis. Typically, the locomotive compressor will supply compressed air once every five minutes for a time of approximately thirty seconds. A
membrane type air dryer if incorporated into the air system of a locomotive would therefore be required to operate according to this duty cycle. During the thirty second period when the compressor is loaded (i.e., the drying phase of the duty cycle), the compressed air that would flow into the fiber bundle would cause pressure to build within the membranes as described previously. When turned off during the inactive phase of its duty cycle, the compressor would be unloaded for such a long time that much, if not most all, of the pressure built up within the membranes would be lost as sweep air. Consequently, when again turned on for the next thirty second period, the compressor would spend too much of that time span on merely re-pressurizing the membranes of the fiber bundle.
The primary disadvantage to this setup is that sweep air is continuously vented from the vessel of the membrane type air dryer. It would therefore be desirable to devise a system that prevents excessive loss of air as sweep air from the sweep air containment vessel of a membrane type air dryer.
OBJECTIVES OF THE INVENTION
It is, therefore, a primary objective of the invention to provide a control system for a membrane type air dryer that reduces the amount of air lost as sweep air by which the water vapor that has passed through the membranes of the air dryer is swept away to atmosphere.
Another objective is to reduce the time that the compressor must take to repressurize the membranes of a membrane type air dryer during the drying phase of its duty cycle.
Yet another objective is to incorporate a memory feature into a membrane type air dryer that enables the air dryer to resume its drying function generally with the same amount of internal air pressure that it had when the drying function was last stopped.
In addition to the objectives and advantages listed above, various other objectives and advantages will become more readily apparent to persons skilled in the relevant art from a reading of the detailed description section of this document. These other objectives and advantages will become particularly apparent when the detailed description is considered along with the attached drawings and with the appended claims.
SUMMARY OF THE INVENTION
In a presently preferred embodiment, the invention provides a control system that reduces the amount of gas lost as sweep gas from a membrane type gas dryer. The membrane gas dryer is of the type that features an inlet end that receives moisture laden gas from a compressor, an outlet end from which dried gas is discharged to a pneumatic component and a drain port from which permeate sweep gas inclusive of permeate water vapor is expelled from the gas dryer. The control system includes a purge valve that is connected to the drain port of the gas dryer and a means for controlling the purge valve. The purge valve has a pilot port that responds to pressure by closing the purge valve thereby preventing the permeate sweep gas from exhausting to atmosphere through the drain port. The means for controlling controls the purge valve such that (i) when the compressor is unloaded, the dried gas from the pneumatic component is allowed to flow to and pressurize the pilot port thereby closing the purge valve and preventing the permeate sweep gas from exhausting to atmosphere and (ii) when the compressor is loaded, the pilot port is vented to atmosphere thereby opening the purge valve and allowing the permeate sweep gas to exhaust to atmosphere via the drain port of the membrane type gas dryer.
~ _~,' CA 02259736 2001-10-10 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view of a membrane type air dryer within the compressed air system of a train locomotive.
Figure 2 is a schematic view of a membrane type air dryer in the compressed air system of a locomotive incorporating the control system according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
Before describing the invention in detail, the reader is advised that, for the sake of clarity and understanding, identical components having identical functions have been marked where possible with the same reference numerals in each of the Figures provided in this document.
Figure 1 illustrates one way in which to incorporate a membrane type air dryer within the compressed air system of a railroad locomotive. The membrane type air dryer 1 features a membrane fiber bundle 2 encased within a containment vessel 3. During the drying phase of the aforementioned duty cycle, the inlet end 4 of the membrane type air dryer 1 receives moisture-laden air from a compressor 20 either directly or indirectly via other air drying components situated between the compressor 20 and the membrane air dryer. Due to the incoming air stream, pressure quickly builds in the membranes of the fiber bundle 2. The sweep air leaks through the membranes carrying with it the permeate water vapor into the sweep air space 9 of vessel 3. From the drain port 6, the sweep air inclusive of the permeate water vapor is expelled to atmosphere. From the outlet end 5 of the air dryer, dried non-permeate air is discharged to a reservoir 7 or other suitable pneumatic components.
Figure 1 also shows a check valve 8 installed between the outlet end 5 of the dryer and the inlet of reservoir 7. The check valve 8 prevents dried air from flowing back into the dryer when the locomotive compressed air system is in the inactive phase of its duty cycle.
During this inactive phase, the pressure that had built up within the membranes of the fiber bundle 2 during the previous drying phase continues to drop becawse sweep air continues to leak through the membranes and to atmosphere via drain port 6 of the sweep air containment vessel 3. As the duty cycle is typically set at thirty seconds of drying once every five minutes, the inactive phase is much longer than the drying phase of the duty cycle. The membranes of the fiber bundle 2 thus lose much, if not all, of their pressure during the inactive phase of the duty cycle. Too much of the next drying phase must then be devoted to repressurizing the membranes of the fiber bundle 2 before the dryer can again operate efficiently.
Referring now to a presently preferred embodiment of the invention, Figure 2 illustrates a control system, generally designated 100, for a membrane type air dryer 1 that overcomes the deficiencies inherent in the design illustrated in Figure 1. The control system 100 includes a purge valve 101, a magnet valve 120 and a pressure switch 130. The purge valve 101 has an inlet: connected to the drain port 6 of containment vessel 3, an outlet exposed to atmosphere and a pilot port 102. In response to a preset pressure received at pilot port 102 from interconnective pipe 12, the purge valve 101 closes communication between its inlet and outlet. When closed due t:o the preset pressure, the purge valve 101 prevents the permeate sweep air from exhausting to atmosphere via drain port 6 of containment vessel 3.
Connected between interconnective pipes 12 and 13, the magnet valve 120 is a three way valve situated between the reservoir 7 and the pilot port 1.02 of purge valve 101.
Specifically, the magnet valve 120 is connected at its supply port 121 to pipe 13 from the main :reservoir 7 and at its delivery port 122 to pipe 12 from t:he pilot port of purge valve 101. The exhaust port 123 of magnet valve 120 is open to atmosphere. Preferably controlled by pressure switch 130 or other suitable device, the magnet valve may be commanded to assume either a normally closed (deenergized) state or an open (energized) state. Figure 2 shows the magnet valve 120 in its normally closed state in which its delivery and exhaust ports 122 and 123 communicate. In its open state (not shown), the supply and delivery ports 121 and 122 communicate. The pressure switch 130 controls the magnet valve 120 by being responsive to the loading of the compressed air system of the locomotive.
Regarding the particulars of how purge valve 101 and magnet valve 120 are controlled, when the compressor 20 is unloaded, the pressure switch 130 energizes the magnet valve 120 via electrical lines 132. The magnet valve 120 responds by assuming the open state _Ln which the supply and delivery ports 121 and 122 communicate. This allows the dried permeate air previously stored in reservoir 7 to flow through pipe 13, magnet valve 120 and pipe 12 to the pilot port 102 of purge valve 101. With its pilot port pressurized, the purge valve 101 closes thereby preventing the permeate sweep air from exhausting to atmosphere via drain port 6 of the sweep air Containment vessel 3. The sweep air is thus retained within the sweep air containment vessel 3 when the compressed air system is unloaded. When the compressor 20 again becomes loaded, the pressure switch 130 deenergizes the magnet valve 120. The magnet valve responds by again assuming its normally closed state in which its delivery and exhaust ports 122 and 123 Communicate. This allows the pilot port 102 to vent to atmosphere through pipe 12 and the internal passageway formed in magnet valve 120 by the aligning of its delivery and exhaust ports 122 and 123.
Without pressure impinging on its pilot port, the purge valve 101 opens thereby allowing the permeate sweep air to exhaust from the drain port 6 to atmosphere.
Taken together, magnet valve 120 and pressure switch 130 may essentially be considered as a means through which to control the purge valve 101 of the invention. It should be understood that this Coni~rol means, of Course, could also be implemented using various other known techniques and devices in lieu of the air piloted purge valve 101, magnet valve 120 and pressure switch 130. The purge valve, for example, could take the form of a magnet valve controlled by such a pressure switch.
By itself, the magnet valve 120 is a device whose construction and operation is generally well known in the air drying art. The pressure switch itself may be of the type commonly used in the field of pneumatics. For example, it is well known that compressors are often equipped with a governor - a mechanism by which to regulate automatically the operation of the compressor. This governor typically features a pressure switch of the type appropriate to this invention.
then the compressor 20 is unloaded, the pressure switch in the governor senses the unloaded state of the compressor 20 and can provide an electrical signal that can be used to energize the magnet valve 120 of the invention.
It should be apparent that the invention could be implemented in a variety of air drying systems and need not be confined solely to railroad industry applications. It is, however, particularly well suited for use with train locomotive compressed air systems that are equipped with membrane type air dryers. This is because train compressed air systems are operated according to the aforementioned two phase duty cycle. Specifically, the control system 100 of the invention essentially endows a membrane type air dryer with a memory feature. This feature enables the air dryer to resume its next drying phase generally with the same amount of internal air pressure that it had when the previous drying phase stopped. This reduces the amount of time that the compressor 20 must take to repressurize the membranes during the next drying phase. More significantly, it reduces the amount of air that the air dryer would otherwise lose as sweep air absent the invention.
The presently preferred embodiment for carrying out the invention has been set forth in detail according to the Patent Act. Those persons of ordinary skill in the art to which this invention pertains may nevertheless recognize various alternative ways of practicing the invention without departing from the spirit and scope of the appended claims.
Those of such skill will also recognize that the foregoing description is merely illustrative and not intended to limit any of the ensuing claims to any particular narrow interpretation.
Accordingly, to promote the progress of science and useful arts, I secure for myself by Letters Patent exclusive rights to all subject matter embraced by the following claims for the time prescribed by the Patent Act.
AIR
FIELD OF THE INVENTION
The invention generally re:Lates to gas dryers of the type that use semipermeable membranes to remove moisture from gas in which the moisture is suspended. More particularly, the invention relates to a system that reduces the amount of gas otherwise lost as sweep gas that is used to sweep the accumulated moisture away from the membranes of the gas dryer.
BACKGROUND OF THE IN'rENTION
The following background information is provided to assist the reader to understand the invention described and claimed below. Accordingly, any terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.
It is well known in the air drying art that the amount of moisture suspended in any given volume of air is dependent on both the pressure and temperature of the air contained in that volume. This relationship between pressure, volume and temperature is defined by the various ideal gas laws of thermodynamics. When a quantity of air is compressed by reducing the volume it occupies, the amount of moisture that the compressed air can hold is reduced accordingly, assuming its temperature is held constant. The temperature of air, however, increases as the air is compressed, and this temperature increase enables the air to hold its moisture.
In most compressed air systems, such as those used in the railroad industry, temperature increases are undesirable. This is because the compressed air system has components downstream whose temperatures may be lower than that of the incoming moisture-laden compressed air. The moisture in such moisture-laden air tends to condense on the surfaces of these downstream components and contaminates the compressed air system and the pneumatic components that it supplies. Consequently, an aftercooler is typically inserted between the output of the compressor and the intake port of the air drying system to lower the temperature of the incoming compressed air. By lowering the temperature, the aftercooler causes some of the water vapor suspended in the air to precipitate out of the air in the form of liquid condensate. This liquid condensate is usually removed from the air drying system via well known devices such as separating chambers and coalescing elements. Despite the use of aftercoolers, separating chambers and coalescing elements, the compressed air will still hold some water vapor as it is difficult to remove this remaining moisture solely by mechanical means. Such mechanical means thus are often used in conjunction with one of the known air drying methods to remove this remaining water vapor. Depending on the specific application and environment in which it is used, an air drying method may be used alone, without the aforementioned mechanical means.
There are at least three prior art methods of drying air that are commonly used to remove water vapor. (1) Absorbent type air dryers use deliquescent desiccant that becomes liquid by absorbing moisture suspended in the air.
Deliquescent air dryers typically have no moving parts and their costs are initially low. These dryers, however, exhibit limited dew point suppression - 20° to 30° F is common. They also require considerable maintenance, e.g., the desiccant must be periodically replaced and the system manually drained on a regular basis. (2) Adsorbent type air dryers use regenerative desiccant that temporarily adsorbs moisture on the surface of its molecules. The moisture temporarily accumulated by the desiccant is later removed via a stream of dried air redirected through the desiccant to purge the moisture to atmosphere. Regenerative dryers are able to achieve low dew points, but impose high costs initially and high operating costs thereafter. Their desiccant towers, in which the desiccant is housed, also must be serviced periodically. (3) Refrigeration type air dryers typically require low maintenance and impose low operating costs, but are not able to achieve low dew points. Dew points are typically limited to approximately 38° F as a minimum to prevent freeze ups. Refrigeration type dryers are used in many industries as a first step in a multi-step drying system, e.g., before drying the air in desiccant type air dryer.
Another method of drying air employs the use of semipermeable membranes to remove moisture from the air in which the moisture is suspended. These membrane type air dryers have long been used in various industries. Such membrane type air dryers typically feature a membrane fiber bundle and a containment vessel or shell in which the bundle is encased. The membrane fiber bundle is of a type that is commercially available from Bend Research, Inc. of Bend, Oregon, U.S.A.
Regarding basic operation of a membrane type air dryer, air passes through each membrane in the bundle by a combination of (i) diffusion through the pores linking the respective surfaces of a membrane and (ii) permeation through the material of the membrane. The force that drives the separation of water vapor from air is the difference between the pressure of the air on one side of a membrane and the pressure of air on the other side of the membrane. When air is compressed, the partial pressures of the various constituents in the air each increase. Water vapor, of course, is present in the stream of compressed air that flows into the inlet of the membrane housing from the source of compressed air. The partial pressure of the water vapor in the air stream flowing in the bundle will be greater than that of the atmospheric air by a factor dependent upon the compression ratio of the compressor. This difference in the partial pressure of water vapor on the inside (higher) versus that on the outside (lower) of the membranes drives the water vapor through the membranes into the sweep air space defined between the outside of the bundle and the inner wall of the containment vessel.
The vessel in which the membrane fiber bundle is encased also features a drain hole that communicates with the sweep air space. The sweep air space serves as the conduit to transport the water vapor that has permeated through the membranes to the drain hole. It is through this drain hole that the permeated water vapor is forcibly purged from the sweep air space by "sweep air." The air stream flowing through the fiber bundle causes pressure to build within its membranes. The "sweep air" that is used to purge the permeated water vapor from the vessel originates within these pressurized membranes. Composed of light gases including even hydrogen and helium that are capable of penetrating the membranes, the sweep air leaks out of the membranes and forcibly carries with it the permeated water vapor out the drain hole in the bottom of the vessel. It is for this reason that the vessel is often referred to as the sweep air containment vessel. The dried non-permeate air that emerges from the outlet of the membrane housing, of course, flows into whatever pneumatic components) that the membrane air dryer is intended to supply.
The membrane type air dryer is typically incorporated within a compressed air system between the source of compressed air and a reservoir or other pneumatic component to which it supplies the compressed dried air. As shown in Figure 1, a check valve is commonly installed between the outlet of the dryer and the inlet of the reservoir to prevent air from flowing back into the dryer when the source of compressed air is unloaded (i.e., turned off). When the source of compressed air is loaded, the compressed air that flows through the fiber bundle will cause pressure to build within the membranes as described previously. It is this pressure that is the source of the sweep air. When the source of compressed air is unloaded, however, the pressure that has accumulated within the membranes is largely lost as sweep air as it is continuously vented from the drain hole of the vessel.
It is well known that on a train locomotive the compressor is controlled so that compressed air is supplied to the air system on a periodic basis. Typically, the locomotive compressor will supply compressed air once every five minutes for a time of approximately thirty seconds. A
membrane type air dryer if incorporated into the air system of a locomotive would therefore be required to operate according to this duty cycle. During the thirty second period when the compressor is loaded (i.e., the drying phase of the duty cycle), the compressed air that would flow into the fiber bundle would cause pressure to build within the membranes as described previously. When turned off during the inactive phase of its duty cycle, the compressor would be unloaded for such a long time that much, if not most all, of the pressure built up within the membranes would be lost as sweep air. Consequently, when again turned on for the next thirty second period, the compressor would spend too much of that time span on merely re-pressurizing the membranes of the fiber bundle.
The primary disadvantage to this setup is that sweep air is continuously vented from the vessel of the membrane type air dryer. It would therefore be desirable to devise a system that prevents excessive loss of air as sweep air from the sweep air containment vessel of a membrane type air dryer.
OBJECTIVES OF THE INVENTION
It is, therefore, a primary objective of the invention to provide a control system for a membrane type air dryer that reduces the amount of air lost as sweep air by which the water vapor that has passed through the membranes of the air dryer is swept away to atmosphere.
Another objective is to reduce the time that the compressor must take to repressurize the membranes of a membrane type air dryer during the drying phase of its duty cycle.
Yet another objective is to incorporate a memory feature into a membrane type air dryer that enables the air dryer to resume its drying function generally with the same amount of internal air pressure that it had when the drying function was last stopped.
In addition to the objectives and advantages listed above, various other objectives and advantages will become more readily apparent to persons skilled in the relevant art from a reading of the detailed description section of this document. These other objectives and advantages will become particularly apparent when the detailed description is considered along with the attached drawings and with the appended claims.
SUMMARY OF THE INVENTION
In a presently preferred embodiment, the invention provides a control system that reduces the amount of gas lost as sweep gas from a membrane type gas dryer. The membrane gas dryer is of the type that features an inlet end that receives moisture laden gas from a compressor, an outlet end from which dried gas is discharged to a pneumatic component and a drain port from which permeate sweep gas inclusive of permeate water vapor is expelled from the gas dryer. The control system includes a purge valve that is connected to the drain port of the gas dryer and a means for controlling the purge valve. The purge valve has a pilot port that responds to pressure by closing the purge valve thereby preventing the permeate sweep gas from exhausting to atmosphere through the drain port. The means for controlling controls the purge valve such that (i) when the compressor is unloaded, the dried gas from the pneumatic component is allowed to flow to and pressurize the pilot port thereby closing the purge valve and preventing the permeate sweep gas from exhausting to atmosphere and (ii) when the compressor is loaded, the pilot port is vented to atmosphere thereby opening the purge valve and allowing the permeate sweep gas to exhaust to atmosphere via the drain port of the membrane type gas dryer.
~ _~,' CA 02259736 2001-10-10 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view of a membrane type air dryer within the compressed air system of a train locomotive.
Figure 2 is a schematic view of a membrane type air dryer in the compressed air system of a locomotive incorporating the control system according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
Before describing the invention in detail, the reader is advised that, for the sake of clarity and understanding, identical components having identical functions have been marked where possible with the same reference numerals in each of the Figures provided in this document.
Figure 1 illustrates one way in which to incorporate a membrane type air dryer within the compressed air system of a railroad locomotive. The membrane type air dryer 1 features a membrane fiber bundle 2 encased within a containment vessel 3. During the drying phase of the aforementioned duty cycle, the inlet end 4 of the membrane type air dryer 1 receives moisture-laden air from a compressor 20 either directly or indirectly via other air drying components situated between the compressor 20 and the membrane air dryer. Due to the incoming air stream, pressure quickly builds in the membranes of the fiber bundle 2. The sweep air leaks through the membranes carrying with it the permeate water vapor into the sweep air space 9 of vessel 3. From the drain port 6, the sweep air inclusive of the permeate water vapor is expelled to atmosphere. From the outlet end 5 of the air dryer, dried non-permeate air is discharged to a reservoir 7 or other suitable pneumatic components.
Figure 1 also shows a check valve 8 installed between the outlet end 5 of the dryer and the inlet of reservoir 7. The check valve 8 prevents dried air from flowing back into the dryer when the locomotive compressed air system is in the inactive phase of its duty cycle.
During this inactive phase, the pressure that had built up within the membranes of the fiber bundle 2 during the previous drying phase continues to drop becawse sweep air continues to leak through the membranes and to atmosphere via drain port 6 of the sweep air containment vessel 3. As the duty cycle is typically set at thirty seconds of drying once every five minutes, the inactive phase is much longer than the drying phase of the duty cycle. The membranes of the fiber bundle 2 thus lose much, if not all, of their pressure during the inactive phase of the duty cycle. Too much of the next drying phase must then be devoted to repressurizing the membranes of the fiber bundle 2 before the dryer can again operate efficiently.
Referring now to a presently preferred embodiment of the invention, Figure 2 illustrates a control system, generally designated 100, for a membrane type air dryer 1 that overcomes the deficiencies inherent in the design illustrated in Figure 1. The control system 100 includes a purge valve 101, a magnet valve 120 and a pressure switch 130. The purge valve 101 has an inlet: connected to the drain port 6 of containment vessel 3, an outlet exposed to atmosphere and a pilot port 102. In response to a preset pressure received at pilot port 102 from interconnective pipe 12, the purge valve 101 closes communication between its inlet and outlet. When closed due t:o the preset pressure, the purge valve 101 prevents the permeate sweep air from exhausting to atmosphere via drain port 6 of containment vessel 3.
Connected between interconnective pipes 12 and 13, the magnet valve 120 is a three way valve situated between the reservoir 7 and the pilot port 1.02 of purge valve 101.
Specifically, the magnet valve 120 is connected at its supply port 121 to pipe 13 from the main :reservoir 7 and at its delivery port 122 to pipe 12 from t:he pilot port of purge valve 101. The exhaust port 123 of magnet valve 120 is open to atmosphere. Preferably controlled by pressure switch 130 or other suitable device, the magnet valve may be commanded to assume either a normally closed (deenergized) state or an open (energized) state. Figure 2 shows the magnet valve 120 in its normally closed state in which its delivery and exhaust ports 122 and 123 communicate. In its open state (not shown), the supply and delivery ports 121 and 122 communicate. The pressure switch 130 controls the magnet valve 120 by being responsive to the loading of the compressed air system of the locomotive.
Regarding the particulars of how purge valve 101 and magnet valve 120 are controlled, when the compressor 20 is unloaded, the pressure switch 130 energizes the magnet valve 120 via electrical lines 132. The magnet valve 120 responds by assuming the open state _Ln which the supply and delivery ports 121 and 122 communicate. This allows the dried permeate air previously stored in reservoir 7 to flow through pipe 13, magnet valve 120 and pipe 12 to the pilot port 102 of purge valve 101. With its pilot port pressurized, the purge valve 101 closes thereby preventing the permeate sweep air from exhausting to atmosphere via drain port 6 of the sweep air Containment vessel 3. The sweep air is thus retained within the sweep air containment vessel 3 when the compressed air system is unloaded. When the compressor 20 again becomes loaded, the pressure switch 130 deenergizes the magnet valve 120. The magnet valve responds by again assuming its normally closed state in which its delivery and exhaust ports 122 and 123 Communicate. This allows the pilot port 102 to vent to atmosphere through pipe 12 and the internal passageway formed in magnet valve 120 by the aligning of its delivery and exhaust ports 122 and 123.
Without pressure impinging on its pilot port, the purge valve 101 opens thereby allowing the permeate sweep air to exhaust from the drain port 6 to atmosphere.
Taken together, magnet valve 120 and pressure switch 130 may essentially be considered as a means through which to control the purge valve 101 of the invention. It should be understood that this Coni~rol means, of Course, could also be implemented using various other known techniques and devices in lieu of the air piloted purge valve 101, magnet valve 120 and pressure switch 130. The purge valve, for example, could take the form of a magnet valve controlled by such a pressure switch.
By itself, the magnet valve 120 is a device whose construction and operation is generally well known in the air drying art. The pressure switch itself may be of the type commonly used in the field of pneumatics. For example, it is well known that compressors are often equipped with a governor - a mechanism by which to regulate automatically the operation of the compressor. This governor typically features a pressure switch of the type appropriate to this invention.
then the compressor 20 is unloaded, the pressure switch in the governor senses the unloaded state of the compressor 20 and can provide an electrical signal that can be used to energize the magnet valve 120 of the invention.
It should be apparent that the invention could be implemented in a variety of air drying systems and need not be confined solely to railroad industry applications. It is, however, particularly well suited for use with train locomotive compressed air systems that are equipped with membrane type air dryers. This is because train compressed air systems are operated according to the aforementioned two phase duty cycle. Specifically, the control system 100 of the invention essentially endows a membrane type air dryer with a memory feature. This feature enables the air dryer to resume its next drying phase generally with the same amount of internal air pressure that it had when the previous drying phase stopped. This reduces the amount of time that the compressor 20 must take to repressurize the membranes during the next drying phase. More significantly, it reduces the amount of air that the air dryer would otherwise lose as sweep air absent the invention.
The presently preferred embodiment for carrying out the invention has been set forth in detail according to the Patent Act. Those persons of ordinary skill in the art to which this invention pertains may nevertheless recognize various alternative ways of practicing the invention without departing from the spirit and scope of the appended claims.
Those of such skill will also recognize that the foregoing description is merely illustrative and not intended to limit any of the ensuing claims to any particular narrow interpretation.
Accordingly, to promote the progress of science and useful arts, I secure for myself by Letters Patent exclusive rights to all subject matter embraced by the following claims for the time prescribed by the Patent Act.
Claims (12)
1. A control system for a membrane gas dryer of the type having an inlet end for receiving moisture laden gas ultimately from a compressor, an outlet end for discharging dried gas to a pneumatic component and a drain port for expelling permeate sweep gas inclusive of permeate water vapor from such gas dryer, said control system comprising:
(a) a purge valve, connected to such drain port of such gas dryer, capable of being closed so as to prevent such permeate sweep gas from exhausting to atmosphere via such drain port; and (b) a means for controlling said purge valve such that (i) when such compressor is unloaded, said means for controlling closes said purge valve and thereby prevents such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said means for controlling opens said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via such drain port of such gas dryer.
(a) a purge valve, connected to such drain port of such gas dryer, capable of being closed so as to prevent such permeate sweep gas from exhausting to atmosphere via such drain port; and (b) a means for controlling said purge valve such that (i) when such compressor is unloaded, said means for controlling closes said purge valve and thereby prevents such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said means for controlling opens said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via such drain port of such gas dryer.
2. The control system for a membrane gas dryer, as claimed in claim 1, wherein (i) said purge valve is gas piloted having a pilot port that responds to pressure by closing said purge valve and (ii) said means for controlling includes:
(a) a magnet valve for interconnecting said pilot port of said purge valve and such pneumatic component when opened and for interconnecting said pilot port and atmosphere when closed; and (b) a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said magnet valve to open thereby allowing flow of such dried gas from such pneumatic component to pressurize said pilot port thereby closing said purge valve and preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said magnet valve to vent said pilot port to atmosphere thereby opening said purge valve and allowing such permeate sweep gas to exhaust to atmosphere via such drain port.
(a) a magnet valve for interconnecting said pilot port of said purge valve and such pneumatic component when opened and for interconnecting said pilot port and atmosphere when closed; and (b) a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said magnet valve to open thereby allowing flow of such dried gas from such pneumatic component to pressurize said pilot port thereby closing said purge valve and preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said magnet valve to vent said pilot port to atmosphere thereby opening said purge valve and allowing such permeate sweep gas to exhaust to atmosphere via such drain port.
3. The control system for a membrane gas dryer, as claimed in claim 2, wherein such pneumatic component is a main reservoir of a train locomotive.
4. The control system for a membrane gas dryer, as claimed in claim 1, wherein:
(a) said purge valve is a magnet valve that responds to energization by closing said purge valve; and (b) said means for controlling includes a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said purge valve thereby preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via such drain port.
(a) said purge valve is a magnet valve that responds to energization by closing said purge valve; and (b) said means for controlling includes a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said purge valve thereby preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via such drain port.
5. The control system for a membrane gas dryer, as claimed in claim 4, wherein such pneumatic component is a main reservoir of a train locomotive.
6. An improvement to a membrane gas dryer of the type having (i) an inlet end for receiving moisture laden gas ultimately from a compressor, (ii) an outlet end for discharging dried gas to a pneumatic component and (iii) a drain port for expelling permeate ,weep gas inclusive of permeate water vapor, said improvement comprising:
(a) a purge valve, connected to said drain port of said gas dryer, capable of being closed so as to prevent such permeate sweep gas from exhausting to atmosphere via said drain port; and (b) a means for controlling said purge valve such that (i) when such compressor is unloaded, said means for controlling closes said purge valve and thereby prevents such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said means for controlling opens said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via said drain port of said gas dryer.
(a) a purge valve, connected to said drain port of said gas dryer, capable of being closed so as to prevent such permeate sweep gas from exhausting to atmosphere via said drain port; and (b) a means for controlling said purge valve such that (i) when such compressor is unloaded, said means for controlling closes said purge valve and thereby prevents such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said means for controlling opens said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via said drain port of said gas dryer.
7. The improved membrane gas dryer, as claimed in claim 6, wherein (i) said purge valve is gas piloted having a pilot port that responds to pressure by closing said purge valve and (ii) said means for controlling includes:
(a) a magnet valve for interconnecting said pilot port of said purge valve and such pneumatic component when opened and for interconnecting said pilot port and atmosphere when closed; and (b) a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said magnet valve to open thereby allowing flow of such dried gas from such pneumatic component to pressurize said pilot port thereby closing said purge valve and preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said magnet valve to vent said pilot port to atmosphere thereby opening said purge valve and allowing such permeate sweep gas to exhaust to atmosphere via said drain port.
(a) a magnet valve for interconnecting said pilot port of said purge valve and such pneumatic component when opened and for interconnecting said pilot port and atmosphere when closed; and (b) a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said magnet valve to open thereby allowing flow of such dried gas from such pneumatic component to pressurize said pilot port thereby closing said purge valve and preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said magnet valve to vent said pilot port to atmosphere thereby opening said purge valve and allowing such permeate sweep gas to exhaust to atmosphere via said drain port.
8. The improved membrane gas dryer, as claimed in claim 7, wherein such pneumatic component is at least one of a main reservoir, an auxiliary reservoir and an emergency reservoir of a train locomotive.
9. The improved membrane gas dryer, as claimed in claim 8, wherein such pneumatic component is such main reservoir.
10. The improved membrane gas dryer, as claimed in claim 6, wherein:
(a) said purge valve is a magnet valve that responds to energization by closing said purge valve; and (b) said means for controlling includes a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said purge valve thereby preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via said drain port.
(a) said purge valve is a magnet valve that responds to energization by closing said purge valve; and (b) said means for controlling includes a pressure switch responsive to loading of such compressor such that (i) when such compressor is unloaded, said pressure switch energizes said purge valve thereby preventing such permeate sweep gas from exhausting to atmosphere and (ii) when such compressor is loaded, said pressure switch deenergizes said purge valve thereby allowing such permeate sweep gas to exhaust to atmosphere via said drain port.
11. The improved membrane gas dryer, as claimed in claim 10, wherein such pneumatic component is at least one of a main reservoir, an auxiliary reservoir and an emergency reservoir of a train locomotive.
12. The improved membrane gas dryer, as claimed in claim 11, wherein such pneumatic component is such main reservoir.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US178,460 | 1998-10-23 | ||
| US09/178,460 US6070339A (en) | 1998-10-23 | 1998-10-23 | Membrane air dryer with scheme to reduce air lost as sweep air |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2259736A1 CA2259736A1 (en) | 2000-04-23 |
| CA2259736C true CA2259736C (en) | 2002-08-13 |
Family
ID=22652622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002259736A Expired - Lifetime CA2259736C (en) | 1998-10-23 | 1999-01-20 | Membrane air dryer with scheme to reduce air lost as sweep air |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US6070339A (en) |
| EP (1) | EP0995480A3 (en) |
| JP (1) | JP3362017B2 (en) |
| AU (1) | AU749819B2 (en) |
| CA (1) | CA2259736C (en) |
Families Citing this family (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19722731A1 (en) * | 1997-04-10 | 1998-10-15 | Beko Kondensat Technik Gmbh | Compressed air drying membrane filter unit |
| AU1364501A (en) * | 1999-11-12 | 2001-06-06 | Porous Media Corporation | Compressed gas systems utilizing a variable pressure membrane air drier, and method of operation thereof |
| JP3816289B2 (en) * | 2000-02-18 | 2006-08-30 | ナブテスコ株式会社 | Hollow fiber membrane dehumidifier |
| JP2001239125A (en) * | 2000-03-01 | 2001-09-04 | Nabco Ltd | Hollow-fiber membrane dehumidifier |
| US6581297B1 (en) | 2000-11-17 | 2003-06-24 | Graham-White Manufacturing Company | Drying apparatus and method |
| US6539728B2 (en) | 2000-12-04 | 2003-04-01 | Amos Korin | Hybrid heat pump |
| US6739142B2 (en) | 2000-12-04 | 2004-05-25 | Amos Korin | Membrane desiccation heat pump |
| US6593525B1 (en) | 2002-03-04 | 2003-07-15 | Andrew Corporation | Direct burial outdoor membrane pressurization system |
| US6719825B2 (en) | 2002-05-07 | 2004-04-13 | Graham-White Manufacturing Company | Air drying apparatus and method |
| US6764529B2 (en) * | 2002-07-01 | 2004-07-20 | Bendix Commercial Vehicle Systems Llc | Membrane gas dehydrating apparatus for gas controlled and powered systems |
| US6881245B2 (en) * | 2002-10-18 | 2005-04-19 | Bendix Commercial Vehicle Systems Llc | Membrane air dryer and method of mounting a membrane dryer to a vehicle |
| US6923845B2 (en) * | 2002-10-18 | 2005-08-02 | Bendix Commercial Vehicle Systems Llc | Membrane air dryer for vehicle air brake system |
| US7153341B2 (en) * | 2003-04-04 | 2006-12-26 | Parker-Hannifin Corporation | Processes for controlling regenerative sweep air for membrane systems |
| EP1627634B1 (en) * | 2003-05-15 | 2013-10-16 | Ajinomoto Co., Inc. | Use of capsinoids for the treatment of arteriosclerosis |
| US7014690B2 (en) * | 2003-12-18 | 2006-03-21 | Westinghouse Air Brake Technologies Corporation | Expandable desiccant element |
| ATE443561T1 (en) * | 2004-09-27 | 2009-10-15 | Duerr Dental Ag | DRYER UNIT FOR COMPRESSED AIR AND OTHER GASEOUS MEDIA |
| JP4860247B2 (en) * | 2005-11-24 | 2012-01-25 | アネスト岩田株式会社 | Purge-controlled polymer membrane air dryer system |
| US7637985B2 (en) | 2006-03-30 | 2009-12-29 | Bendix Commercial Vehicle Systems Llc | Dry compressed air supply module |
| US7517388B2 (en) * | 2006-05-15 | 2009-04-14 | Generon Igs, Inc. | Air separation membrane module with variable sweep stream |
| US20070277673A1 (en) * | 2006-06-06 | 2007-12-06 | Crowder Robert O | Sweep control for membrane dryers |
| US7678177B2 (en) * | 2006-09-12 | 2010-03-16 | New York Air Brake Corporation | Membrane air dryer and sweep valve |
| US7731784B2 (en) * | 2006-10-11 | 2010-06-08 | New York Air Brake Corporation | Membrane air dryer with sweep air control |
| US7938884B2 (en) * | 2007-01-31 | 2011-05-10 | Spx Corporation | Integral sweep controller for gas membrane separation device |
| US20080223212A1 (en) * | 2007-03-16 | 2008-09-18 | Crowder Robert O | Reducing moisture content of compressed air |
| US8066801B2 (en) * | 2007-04-24 | 2011-11-29 | New York Air Brake Corporation | Sweep air system for membrane air dryer |
| US20090049983A1 (en) * | 2007-08-22 | 2009-02-26 | Flair Corporation, A Delaware Corporation | Energy management system for membrane separation device |
| US8268055B2 (en) * | 2010-02-25 | 2012-09-18 | Perma Pure Llc | Membrane gas dryers incorporating rotatable fittings |
| CN102740952B (en) * | 2010-02-25 | 2014-04-09 | 帕玛普乐有限责任公司 | Membrane gas dryers incorporating rotatable fittings |
| JP6622184B2 (en) * | 2014-02-27 | 2019-12-18 | ナブテスコオートモーティブ株式会社 | Compressed air drying system |
| US11333477B2 (en) | 2015-04-27 | 2022-05-17 | Drywall Devil, Llc | Tape measure device and attachment for measuring and cutting drywall |
| KR102602424B1 (en) * | 2018-10-11 | 2023-11-14 | 현대자동차주식회사 | System and method for removing residual pressure in the motor driven air compressor management system |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4549888A (en) * | 1984-11-07 | 1985-10-29 | Allied Corporation | Automatic control for an external air supply |
| US4783201A (en) * | 1987-12-28 | 1988-11-08 | Rice Arthur W | Gas dehydration membrane apparatus |
| GB8830107D0 (en) * | 1988-12-23 | 1989-02-22 | Boc Group Plc | Gas separation |
| US5059374A (en) * | 1989-02-09 | 1991-10-22 | The Dow Chemical Company | Method for sealing a hollow fiber membrane module in a case |
| US5013331A (en) * | 1989-06-30 | 1991-05-07 | E. I. Du Pont De Nemours And Company | Permeator with selectable flow rates |
| US5176725A (en) * | 1991-07-26 | 1993-01-05 | Air Products And Chemicals, Inc. | Multiple stage countercurrent hollow fiber membrane module |
| US5681368A (en) * | 1995-07-05 | 1997-10-28 | Andrew Corporation | Dehumidifier system using membrane cartridge |
| US5605564A (en) * | 1996-02-14 | 1997-02-25 | Howell Laboratories, Inc. | Membrane gas dehydrator |
-
1998
- 1998-10-23 US US09/178,460 patent/US6070339A/en not_active Expired - Lifetime
-
1999
- 1999-01-20 CA CA002259736A patent/CA2259736C/en not_active Expired - Lifetime
- 1999-09-30 AU AU52587/99A patent/AU749819B2/en not_active Ceased
- 1999-10-06 EP EP99119755A patent/EP0995480A3/en not_active Withdrawn
- 1999-10-25 JP JP30232099A patent/JP3362017B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| AU5258799A (en) | 2000-05-04 |
| CA2259736A1 (en) | 2000-04-23 |
| US6070339A (en) | 2000-06-06 |
| EP0995480A3 (en) | 2001-10-17 |
| JP3362017B2 (en) | 2003-01-07 |
| AU749819B2 (en) | 2002-07-04 |
| JP2000126538A (en) | 2000-05-09 |
| EP0995480A2 (en) | 2000-04-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2259736C (en) | Membrane air dryer with scheme to reduce air lost as sweep air | |
| CA2234776C (en) | Combination main reservoir and air system | |
| CA2023608C (en) | Dehumidifier for waveguide system | |
| US5118327A (en) | Dehumidifier for supplying gas having controlled dew point | |
| CA2390474C (en) | Compressed gas systems utilizing a variable pressure membrane air drier, and method of operation thereof | |
| CA2203305C (en) | Regenerative desiccant air dryer | |
| US5681368A (en) | Dehumidifier system using membrane cartridge | |
| EP0599149B1 (en) | Dehumidifier for supplying air using variable flow rate and variable pressure in a membrane dryer | |
| US20070277673A1 (en) | Sweep control for membrane dryers | |
| KR100623585B1 (en) | Vehicle air braking systems | |
| JP3723083B2 (en) | Compressed air supply device | |
| MXPA99009718A (en) | Membrane air dryer that has a regulation reduces air loss as barr air | |
| JP4300495B2 (en) | Gas dehumidifier | |
| JP4110782B2 (en) | Ozone generator | |
| JPH0283015A (en) | Gas dehumidification | |
| JP2000334253A (en) | Compressed air supply device for station service | |
| JP2000279743A (en) | Air system | |
| JPH0871354A (en) | Intermittent operation method of membrane type air dryer and purge circuit thereof | |
| JPH06201231A (en) | Device for removing moisture contained in refrigerant | |
| KR20230108047A (en) | Dehumidification apparatus and dehumidification method of switching type dependent on the amount of water | |
| JP2003090896A (en) | Boiling water reactor power plant | |
| JP2003251135A (en) | Dehumidifying apparatus |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20190121 |